Political figures routinely get their quotations wrong. No modern politician has stood out quite so much in this regard as John F. Kennedy. JFK loved to pepper his speeches and public statements with quotations. This not only perked up his prose, but improved his press by giving him an air of erudition. Kennedy was also, however, a misquoter of eloquence, who showed how creative and unreliable memory can be when using comments others have uttered.

Kennedy’s main resource for quotations was his own memory and the notebook in which he’d jotted quotations and other material for years — some drawn from books he’d read, but most from his mind. According to his speechwriter Theodore Sorensen, Kennedy “was the chief source of his own best quotations.” As a result, he was an endless source of half-remembered quotations that his aides and Library of Congress staff members scurried to try to confirm.

With such a haphazard approach, JFK was not always as knowledgeable as he tried to sound. Before his wife, Jacqueline, corrected him, Kennedy combined lines by Ralph Waldo Emerson and Robert Frost to conclude some of his speeches by saying:

I’ll hitch my wagon to a star (Emerson)

But I have promises to keep (Frost)

And miles to go before I sleep (Frost)

Even though JFK routinely garbled his quotations, it took us years to figure this out. Meanwhile, the young president launched any number of misworded, misattributed or completely mystifying quotations into the public conversation that have stuck around to this day.

The most glaring example is “The only thing necessary for the triumph of evil is that good men do nothing,” which Kennedy attributed to British philosopher Edmund Burke and which recently was judged the most popular quotation of modern times in a poll conducted by editors of “The Oxford Dictionary of Quotations.” Even though it is clear by now that Burke is unlikely to have made this observation, no one has ever been able to determine who did.

Some of Kennedy’s most famous phrases turned out to have long, unacknowledged pedigrees. “The New Frontier,” a phrase in Kennedy’s 1960 acceptance speech that he later used to describe his domestic agenda, was the title of a chapter in a 1936 book written by Kansas Governor Alfred M. Landon, who ran for president as a Republican that year. Two years before that, Franklin D. Roosevelt’s future vice president, Henry Wallace, had written a book titled “New Frontiers.”

The most stirring line of JFK’s inaugural address, “Ask not what your country can do for you, ask what you can do for your country,” echoed similar exhortations made by many others, including Oliver Wendell Holmes Jr. and President Warren G. Harding, who told the 1916 Republican convention, “We must have a citizenship less concerned about what the government can do for it and more anxious about what it can do for the nation.”

The inspiration for Kennedy’s famous observation, “For of those to whom much is given, much is required” can be found in Luke 12:48: “For unto whomsoever much is given, of him shall be much required.”

And when the United States made Winston Churchill an honorary citizen in 1963, Kennedy said of Britain’s former prime minister: “He mobilized the English language and sent it into battle.” Nine years earlier, journalist Edward R. Murrow had said of Churchill, “He mobilized the English language and sent it into battle to steady his fellow countrymen and hearten those Europeans upon whom the long dark night of tyranny had descended.”

Even when he did cite his sources, Kennedy routinely got them wrong. For example, “The hottest places in hell are reserved for those who in a period of great moral crisis maintain their neutrality” is a quotation he attributed to Dante. Dante did say some things about hell, but this wasn’t among them. On another occasion, Kennedy quoted Emerson as having said, “What we are speaks louder than what we say,” a condensation of Emerson’s actual thought: “Don’t say things. What you are stands over you the while, and thunders so that I cannot hear what you say to the contrary.”

Journalist Sander Vanocur said Kennedy liked to quote British statesman Lord Morley’s observation that “Life in politics is one continuous choice between second bests.” No source can be found for this attribution. To make the point that we must plan not just for our time but for posterity, Kennedy would often quote “the great French Marshal Lyautey” who, he said, once asked his gardener to plant a tree. When the gardener cautioned that the tree wouldn’t mature for a century, JFK said the marshal replied, “In that case there is no time to lose, plant it this afternoon.” Library of Congress researchers couldn’t verify this story.

Nor could they find in Nikita Khrushchev’s speeches or writings, “The survivors will envy the dead,” an observation about nuclear war that Kennedy attributed to the Soviet premier during a 1963 news conference. (Three years before Kennedy so quoted Khrushchev, military strategist Herman Kahn had published a book on nuclear war in which he repeatedly asked, “Will the living envy the dead?”)

But Kennedy did launch, if not originate, a number of comments that became standard parts of our lexicon. In a 1961 executive order, he referred to the need for “affirmative steps.” This was the precursor to what came to be known as affirmative action. JFK also was the first U.S. official to talk about “light at the end of the tunnel” with reference to Vietnam, though the phrase was hardly original to him. And in a mid-1963 speech, Kennedy referred to the economic notion that “a rising tide lifts all boats,” prefacing this thought with the words: “As they say on my own Cape Cod . . .”

Without claiming they were his own words, Kennedy put a number of quotations into play that were subsequently attributed to him. When taking responsibility for the Bay of Pigs fiasco, he said, “There’s an old saying that victory has a hundred fathers and defeat is an orphan.” (This saying had appeared in the published 1942 diary of Italian dictator Benito Mussolini’s foreign minister, then in the 1951 movie “The Desert Fox.”) Similarly, in a 1961 speech, Kennedy said, “Somebody once said that Washington was a city of Northern charm and Southern efficiency,” another now routinely credited to him, though of unknown origin.

One quip by JFK that has no known antecedent is his comment at a 1962 White House dinner for Nobel Prize winners: “I think this is the most extraordinary collection of talent, of human knowledge, that has ever been gathered together at the White House — with the possible exception of when Thomas Jefferson dined alone.” Historian Arthur Schlesinger Jr. told author Thurston Clarke that his draft of Kennedy’s speech for this dinner had included a tortured passage on Jefferson’s many talents and achievements, and that Kennedy himself came up with the pithier, more memorable remark.